Buoyancy Flux

Buoyancy flux is the rate at which buoyancy is added to or removed from a water column across an interface, combining the contributions of heat and freshwater (salt) forcing. It is written B = (g/rho)(alpha Q/c_p - rho beta_S (E-P) S), where alpha is thermal expansion, beta_S haline contraction, Q the heat flux, and (E-P) the evaporation minus precipitation. A negative surface buoyancy flux (cooling or net evaporation) destabilizes the column and drives convection and mixed-layer deepening; positive flux restratifies it. Surface buoyancy loss in the Labrador and Nordic seas sets deep-water formation and the overturning.